This invention relates to expandable downhole tubing. In particular, the invention relates to coupling or connecting expandable downhole tubing. One aspect of the invention relates to a method of locating a section of expandable tubing in a bore.
Expandable tubing for use in downhole applications is described in WO93/25800, the disclosure of which is incorporated herein by reference. The tubing is useful as, for example, borehole liner or as a sandscreen support, the use of expandable tubing in sandscreens being more fully described in WO97/17524, the disclosure of which is also incorporated herein by reference. In one application, a section of expandable tubing is positioned in an unlined section of bore intersecting a hydrocarbon-bearing is formation, below an existing bore casing and bore liner. The tubing is then expanded, preferably into contact with the bore wall. The expanded liner supports the bore wall while allowing oil and gas to pass from the formation into the bore. In another application, an expandable well screen is provided, the screen comprising perforated filter sheets mounted on an expandable slotted carrier tube and within a coaxial expandable slotted protective tube. The well screen is expanded downhole to such a size that the protective tube can be set against the surrounding formation.
For locating expandable tubing in a bore it would be preferable to provide a secure connection between the upper end of the expandable tubing and the lower end of an existing bore liner; simply locating the tubing in the liner, with no mechanical connection therebetween, may result in an offset between the two, creating an irregularity on which tools may snag and an unwanted gap through which fluid may flow.
U.S. Pat. No. 3,353,599 discloses a method for securing ends of expandable liner to solid surrounding tubing by means of plastic impregnated glass filter mats. However, the applicant considers that this method would encounter many difficulties in this particular application due to, for example, contamination of the mats by the fluid in the bore and the possibility of the mats being dislodged or damaged during installation of the liner and the expandable tubing, or during other downhole operations.
It is among the objectives of the present invention to obviate or mitigate these disadvantages.
According to the present invention there is provided a method of coupling a section of expandable tubing, the method comprising the steps:
providing a length of expandable tubing and a length of larger diameter non-expanding tubing;
connecting an end portion of said expandable tubing to an end portion of said non-expanding tubing with a portion of expandable tubing;
running the tubing into a bore; and
expanding the expandable tubing.
According to a further aspect of the present invention there is provided a tubing assembly comprising a length of expandable tubing, a length of larger diameter nonexpanding tubing, and a connecting portion of expandable tubing connecting an end portion of the expandable tubing to an end portion of the non-expanding tubing.
These aspects of the invention facilitate connection of a length of expandable tubing to a length of nonexpanding tubing.
The expandable tubing may be a borehole liner or support, or may form part of an expandable well screen or sand screen.
The non-expanding tubing may be a solid connector or coupling, and thus may be a solid connector for joining two lengths of expandable tubing. In particular, this embodiment of the invention permits expandable well screen or sand screen sections to be connected using solid connectors, obviating the difficulties involved in connecting such well screen sections utilising expandable connectors.
The connecting portion may be formed by partially expanding an end of the expandable tubing to a diameter corresponding to the non-expanding tubing. Alternatively, the non-expanding tubing may have an expandable tapering end portion which forms the connecting portion, the smaller diameter end of the tapering portion being of a diameter corresponding to the expandable tubing.
The connecting portion may be welded to one or both of the expandable tubing and the non-expanding tubing. Alternatively, the connection may be provided by other means, such as screw threads, pins, screws, rivets or radially movable keys or fingers engaging corresponding profiles.
According to another aspect of the present invention there is provided a method of locating a section of expandable tubing in a bore, the method comprising the steps:
providing a length of expandable tubing and a length of larger diameter non-expanding tubing;
connecting an end portion of said expandable tubing to an end portion of said non-expanding tubing with a portion of expandable tubing;
running the connected tubing into a bore;
fixing said non-expanding tubing in the bore; and
expanding the expandable tubing.
According to a still further aspect of the present invention there is provided a tubing assembly comprising a length of expandable tubing, a length of larger diameter non-expanding tubing including means for connecting the non-expanding tubing to further tubing located in a bore, and a connecting portion of expandable tubing connecting an end portion of the expandable tubing to an end portion of the non-expanding tubing, the arrangement being such that, in use, the connected tubing may be run into a bore as a unit.
Thus, in these aspects of the present invention, the expandable tubing is connected to the non-expanding tubing on surface, prior to running the expandable tubing into the bore and prior to expansion of the tubing. The non-expanding tubing may be fixed in the bore by any suitable connecting means, typically by connection to an existing section of bore liner or casing. The connection may utilise, for example, a liner hanger, a packer, cooperating screw threads or radially movable keys engaging corresponding profiles.
The expandable tubing may be a borehole liner or support, or may form part of an expandable well screen or sand screen.
The connecting portion may be formed by expanding an upper end of the expandable tubing to a diameter corresponding to the non-expanding tubing. Alternatively, the non-expanding tubing may have an expandable tapering lower end portion which forms the connecting portion, the smaller diameter end of the tapering portion being of a diameter corresponding to the expandable tubing.
Preferably also, the assembly includes a running tool including means for releasably mounting the tubing thereon. The mounting means may be released utilising one of, or a combination of, mechanical force and fluid pressure. Preferably also, the running tool incorporates means for expanding the expandable tubing, which means may be a cone or mandrel which will expand the tubing when pushed or pulled therethrough. Most preferably, the expanding means is initially located within the connecting portion.
The connecting portion may be welded to one or both of the expandable tubing and the non-expanding tubing. Alternatively, the connection may be provided by other means, such as screw threads, pins, screws, rivets or radially movable keys or fingers engaging corresponding profiles.